Parameters for milk pasteurization were established a long time ago, considering the thermal resistance of Mycobacterium bovis, and the systematic adoption of this process has drastically reduced the incidence of human tuberculosis caused by this pathogen. However, more recently, molecular methods have allowed the identification of genetic variations in this bacterium that may lead to greater thermal resistance. The aim of this study was to investigate whether genetic variation leads to variation in the death pattern of this bacterium during the milk pasteurization process. Samples of UHT (ultrahigh temperature)-treated whole milk were artificially contaminated with four different Mycobacterium bovis spoligotypes and were subjected to pasteurization by low-temperature long-time (LTLT) and high-temperature short-time (HTST) treatments. The M. bovis spoligotypes were quantified (Colony Forming Unit per milliliter of milk) before and during the thermal process. The decay of the pathogen was quantified by calculating the difference between the measurements at the beginning and at the end of the thermal treatment. The data demonstrated that the LTLT and HTST pasteurization processes considerably reduced the M. bovis load in the milk; however, the bacterium was not eliminated. There was no difference in the thermal resistance of the spoligotypes tested or in the efficiency of pasteurization processes (LTLT versus HTST). However, heating phase was more effective in reducing the M. bovis load than the target temperature maintenance phase. Key words: Batch pasteurization. Bovine tuberculosis. Flow pasteurization. Mycobacterium bovis. Thermal death. ResumoOs parâmetros para a pasteurização do leite foram estabelecidos há muito tempo, considerando a resistência térmica de Mycobacterium bovis e a adoção sistemática deste processo reduziu drasticamente a incidência de tuberculose humana causada por este patógeno. Entretanto, mais recentemente, métodos moleculares permitiram a identificação de variações genéticas nesta bactéria que podem levar a uma maior resistência térmica. O objetivo deste estudo foi investigar se a variação genética apresenta modificação no padrão de morte da bactéria durante o processo de pasteurização do leite. Amostras de leite tratadas por UHT (ultra-alta temperatura) integral foram contaminadas com quatro diferentes espoligotipos de Mycobacterium bovis e foram submetidos ao tratamento por temperatura baixa e tempo longo (LTLT) e temperatura alta e tempo curto (HTST). Os espoligotipos M. bovis foram quantificados (Unidades Formadoras de colônias por mililitro de leite) antes e durante o processo térmico. A diminuição do patógeno foi quantificada através do cálculo da diferença entre as medições no início e no fim do tratamento térmico. Os dados demonstraram que os processos de pasteurização HTST e LTLT reduziram consideravelmente a carga de M. bovis no leite; no entanto, a bactéria não foi eliminada. Não houve diferença na resistência térmica dos espoligotipos testados nem na eficiência dos pr...

AGRADECIMENTOSMycobacterium bovis causes zoonotic tuberculosis disease that affects animals and humans and can cause death, the milk is an important route of disease transmission to humans. The pasteurization of milk is the main measure to break the transmission chain, whose time and temperature parameters were defined by experiments dating from the late nineteenth century, based on thermal resistance of M. bovis and Coxiella burnetti, considered then the most resistant non-spore-forming pathogens that contaminate the milk. In Brazil, there are two approved binomials 62 ° C to 65 ° C for 30 minutes and 72 ° C to 75 ° C for 15 to 20 seconds.However, over the years and the emergence of new technologies (PCR, spoligotyping and other biomolecular techniques) was observed genetic differences intra-species. Thus, this project aims to evaluate and compare the behavior of two spoligotypes of M. bovis (SB0120 and SB1033) compared to the two pasteurization protocols used in the country. To this end, UHT milk was contaminated with these spoligotypes and subjected to two thermal processes in a water bath. The milk was streaked on solid medium Stonebrink-Leslie and colony counting was done after 45 days of incubation at 37 ° C. This experiment showed that there was no difference between the thermal resistances of the two spoligotypes, however it was detected a greater importance of the heating phase in reducing the agent that the maintenance phase of temperature for the two spoligotypes, in both cases.